Colored contact lenses are used to change the color of the eyes of the wearer and there are currently two dominant methods for coloring such lenses. In one method successive layers of coloring are applied to the inner surface of the mold in which the lens is formed before it is filled with this liquefied resin that hardens into a lens. In the second method, a plurality of colored inks are successively applied to the outer surface of the formed contact lens.
Since eye contact is an important element of human interaction it is important that a colored contact lens impart true texturing to the coloring of the eye of a wearer, and therefore the pattern of coloring in the contact lens must duplicate as closely as possible the complex pattern of colors of the human eye. To create such a complex pattern a plurality of colors, each with a pattern of very fine lines, are applied to the surface of each lens or to the surface of a mold used to form a lens. To create the pattern for each color, a cliche is formed with the pattern of lines etched in the surface of the cliche. Colored ink is then applied into the etchings of the cliche, and when a print pad is subsequently pressed against the surface of the cliche, the ink in the etchings of the cliche is transferred to the surface of the print pad. After the pattern has been applied to the surface of the print pad, the print pad is pressed against the smooth surface of a contact lens or a contact lens mold to transfer the ink from the print pad to the smooth surface thereof.
The pigment which makes up the coloring of the inks used to color contact lenses alter the characteristics of the ink in which it is carried and therefore the characteristic of the ink of each color is somewhat different from that of any other. The surfaces of the contact lenses and of the mold or casting cups used to form such contact lenses are exceeding smooth metal, plastic, glass or crystalline substrate, all of which are traditionally difficult material for receiving inks. A print pad which is suitable for retracting a delicate pattern of ink from a cliche and transferring that pattern to the surface of a contact lens must have a textured surface in which the degree of texturing must be carefully controlled. A print pad which does not have the proper texturing evenly applied across its useable surface will cause the inks applied to become blotted, smeared, or to be incompletely transferred.
The machines which apply coloring to contact lenses can color many thousands of lenses each day and the life expectancy of a print pad used on such machines is approximately one day. The manufactures of colored contact lenses, therefore, have a continuous need for print pads having the texturing required to properly apply coloring to contact lenses.
To obtain print pads having the needed degree of texturing the silicone print pads are formed in metal molds having polished inner surfaces such that the finished print pads have a smooth, glossy surface. The surfaces are subsequently mechanically textured using a proven texturing procedure. One such procedure is to run in a new print pad, that is, put the print pad to use for a period of time, usually fifteen to thirty minutes, until the surface thereof becomes sufficiently worn that it will properly transfer ink. Although the pad can be properly textured by “running it in,” the process is time consuming and it greatly reduces the efficiency of the machine that applies color to the lenses.
In another process the surface mechanically scuffed to obtain the degree of texturing required for applying inks to contact lenses. When texturing is mechanically imparted to the surface the print pad in mounted for rotation about it axis and an abrasive surface is contacted to the surface of the print pad. Such mechanical texturing results in a pattern of elongate scratches which wrap around the circumference of the print pad. When textured print pad having a pattern of linear score lines thereon is used to print on a hard smooth surface, such as metal, plastic, glass or crystalline substrate, the pattern of ink applied lacks clarity. The cost of manufacturing a print pad for applying coloring to contact lenses could, therefore, be greatly reduced if the mold which forms the surface of the print pad can also apply the needed texturing thereto.
There have been prior efforts to manufacture molds in which the print pad are formed, with the inner surface of the molds having a texturing such that when the formed print pad is retracted from the mold with the outer surface thereof textured. This method, however, has failed to result in print pads with the consistency of the texturing needed (even distribution of peaks and valleys, all within the desired range of magnitude) to properly transfer ink to a hard surface. Until the present invention, therefore, no suitable method has been found to apply the desired texturing to the surface of the print pad.